LMP1 also upregulates CSC markers such as CD44 and ATP-binding cassette superfamily G member 2 (ABCG2), and increases the number of side population cells, self-renewal properties, and the tumorigenicity of NPC cells through the PI3K/AKT signaling pathway [47,48,49]. Here, ABCG2 is linked to nasopharyngeal carcinoma.